Overvoltage Mitigation in LVDC Distribution System Caused by DC Circuit Breaker Connected with Constant Power Load

The operation of a high-speed DC circuit breaker can cause overvoltage transients in the Low Voltage Direct Current (LVDC) distribution system especially when the load is driving constant power. If adequate damping is not provided, then the destabilizing effect of constant power load (CPL) can drive the system towards instability. This paper presents a new method to mitigate the over-voltage transients caused by the operation of a DC circuit breaker in an LVDC system. The proposed method is based on utilizing the existing Energy Storage System (ESS) in the DC grid to limit the switching over-voltage within the safe limits. In this study, supercapacitor sizing is performed, while considering the instability problems of the CPLs. First, an analytical expression is built to determine the required value of the supercapacitor, for a basic LVDC distribution system is first considered, state-space modeling methodology is then provided to extend the suggested method for a detailed LVDC distribution system. The Control System Toolbox of the MATLAB program is used for simulations. MATLAB/Simulink time-domain models are also developed to triangulate the theoretical findings. The effectiveness of the proposed model is validated by simulation results.